Preparation And Characteristics Of Chitosan /Poly(Vinyl Alcohol) Blend Ultrafine Fibers By Electrospinning

Electrospinning is a process that produces continuous polymer fibers with diameters in the range of nanometer to micrometer. Electrospun nanofibrous-mats, due to several useful properties such as high specific surface area, low diameter and high porosity, offer a versatile platform for a broad range of applications such as tissue engineering, sensor and fiber templates for the preparation of functional nanotubes. The blend ultrafine fibers of chitosan(CS)/poly(vinyl alcohol)(PVA) were successfully prepared by electrospinning and the study of the electrospun blend ultrafine fibers included the following four aspects:1. The effects of CS/PVA blend solution concentration, viscosity,conductivity,mass ratio and the internal diameter of syringe needle , voltage and distance from the tip of syringe needle to collector on the diameter of the ultrafine fibers formed were investigated by scanning electron microscope (SEM). Furthermore, photocurable monomer triethylene glycol dimethylacrylate (TEGDMA) and photoinitiator 2-hydroxy-2-methyl-1-phenylpropan-1- one (1173) were induced into the CS/PVA blend solution to increase the fiber water-resistance.2. Basing on the basic principles of biomineralization, calcium carbonate (CaCO₃) and CS/PVA composite membranes materials were prepared by mineralized of CaCO₃ on CS/PVA nanofibrous-mats under dynamic condition. The nanofibrous membrane of CS/PVA with small amount of Ca²⁺ was prepared by electrospinning. Then the mimetic nucleation and growth of CaCO₃ crystals on the nanofibers took place in supersaturated CaCO₃ solution. The morphology and structure of membranes were characterized by SEM, X-ray diffraction (X-ray) and Fourier transform infrared spectroscopy (FTIR).3. Antiseptic nanofibrous-mats of chitosan/ poly(vinyl alcohol) loaded with ofloxacin were prepared by electrostatic spinning. The structure and morphology of the nanofibrous-mats were characterized by FTIR,X-ray diffraction and SEM. Nanofibrous-mats which obtained from CS/PVA weight ratios 7:1 and ofloxacin 4% were used to investigated the sustained release behaviors at different PH medium.4. The aligned electrospun nanofibers were prepared in the presence of an applied external direct current(DC) field.The results were summarized as following:(1) the electrospun CS/PVA fibers could successfully produced via elelctrospinning. The viscosity, CS/PVA mass ratio were the main factors influencing the spinnability of CS/PVA solution and morphology of the electrospun CS/PVA. The diameter of the electrospun fibers increased with the increase of solution concentration, whereas increasing the diameter of the sprayer decreased the diameter of the fibers. The water-resistant of fibers was obviously improved by interfiber-photocrosslinking when the CS/PVA weight ratios was 8:2 and the concentration of TEGDMA and HMPP were 4wt% and 0.12wt%. The average diameter of fibers obtained with this method was 200nm.(2) the CS/PVA nanofibers produced CaCO₃ island crystals which interlaced with the CS fiber not only on the surface of the membrane but also in the membrane. These crystals could develop into a continuous CaCO₃ membrane on the fibers at latter stage of mineralization. The obtained crystals were mainly calcite type of CaCO₃.(3) the average diameter of the hybrid chitosan, poly (vinyl alcohol) and ofloxacin fibers obtained was about 200nm, and there was good compatibility among chitosan, poly(vinyl alcohol) and ofloxacin moleculars in the blended nanofibrous-mats from FTIR, XRD analyses. The release time of ofloxacin from the hybrid nanofibrou -mats could be as long as 6 h at PH 7.40.(4) the (SEM) photos showed the arranged nanofibers from both the water-soluble polymer and the oil-soluble polymer could be obtained through the action of an applied external DC field.